The present invention relates to an inspection method of a continuously variable transmission belt which is laid on a driving pulley and a driven pulley of a continuously variable transmission, and controls the diameter ratio of these two pulleys in order to change continuously the transmission gear ratio of a vehicle such as an automobile. More specifically, the invention relates to an inspection method of a continuously variable transmission belt which is assembled through the process of laminating a number of metal elements punched into predetermined shapes, and supported by laminated body thereof on a metal endless belt (hereinafter referred to as xe2x80x9csteel beltxe2x80x9d).
FIGS. 4A and 4B show the appearance of a continuously variable transmission belt. In the drawings, a continuously variable transmission belt 1 is assembled to form an assembly by supporting an element laminated body 3 constituted of a number of (e.g., about 400) metal elements 3a on two runs of belt laminated body 2 consisting of a plurality of (e.g., 12) steel belts 2a. 
The metal element 3a is a steel block (small metal piece) formed in a predetermined shape by a metal punching plate process. For example, it is formed in a shape which brings to mind the upper half image of a human body, i.e., a shape which has a xe2x80x9chead part 3bxe2x80x9d, a xe2x80x9cbreast part 3cxe2x80x9d and a xe2x80x9cneck part 3dxe2x80x9d interconnected by the head part 3b and the breast part 3c. 
A projection 3e is formed on one surface (front surface of the drawing) of the head part 3b, and a recess (not shown) is formed on the other surface (backside of the drawing). Projections 3e and recesses of adjacent metal elements 3a are fitted together to align the metal elements 3a with each other.
Two runs of belt laminated body 2 are fitted into recess 3f formed between the head part 3b and the breast part 3c of the metal element 3a. Here, the number of laminations is set for the belt laminated body 2 so that when the space between the head part 3b and the breast part 3c (spacing width of the recess 3f) is xe2x80x9cLxe2x80x9d, the lamination thickness D of the belt laminated body 2 becomes a value approximately equal to or slightly smaller than L.
As shown in FIG. 5, the continuously variable transmission belt 1 which has the aforementioned constitution is laid on a driving pulley 4 (driving side pulley or input side pulley) and a driven pulley 5 (driven side pulley or output side pulley) of a continuously variable transmission to be used. The continuously variable transmission continuously changes the transmission gear ratio of a vehicle such as an automobile by controlling the diameter ratio of the two pulleys 4, 5. That is, the speed is reduced when the relation between the diameter of the driving pulley 4 (one curvature Ri of the continuously variable transmission belt 1) and the diameter of the driven pulley 5 (other curvature Ro of the continuously variable transmission belt 1) is set to xe2x80x9cRi less than Roxe2x80x9d, the speed is increased at xe2x80x9cRi greater than Roxe2x80x9d, and the speed becomes constant at xe2x80x9cRi=Roxe2x80x9d.
Incidentally, the continuously variable transmission belt 1 is an important transmission component for conveying the driving force of a vehicle, such as an automobile, to the drive train. Especially, in a vehicle installed with a high powered engine, since a considerably large force is applied to the continuously variable transmission belt 1, sufficient consideration must be given to the durability of the continuously variable transmission belt 1.
Thus, Japanese laid-open (Kokai) patent application number (A) 2001-21007 titled xe2x80x9cBELT FOR CONTINUOUSLY VARIABLE TRANSMISSIONxe2x80x9d indicates a technical problem that friction and the pressing force generated between the metal element 3a and the steel element 2a during transmission of the driving force shorten the fatigue life of the steel belt 2a, adversely affecting the durability of the continuously variable transmission belt 1, and discloses that in order to solve the problem, it is effective to devise a shape of the prescribed component of the metal element 3a (see saddle part 3g of FIG. 2A) which contacts with the steel belt 2a. 
However, the technology disclosed in the aforementioned publication is applied only when the metal element 3a is being fabricated. Thus, even if an ideal machining shape can be designed, it is only a paper plan. In an actually manufactured component (metal element 3a), abnormal shaped portions (xe2x80x9cflashesxe2x80x9d, xe2x80x9cburrsxe2x80x9d, xe2x80x9cchipsxe2x80x9d, xe2x80x9cswellsxe2x80x9d, etc.) undeniably occur due to a punching error or the like. Even if precision punching work such as fine blanking process is carried out, since it is difficult to completely eliminate the abnormal shaped portions, for example, some remnants adhere to the punching xe2x80x9cdiexe2x80x9d, and these remnants may form very small abnormal shaped portions on the peripheral part of the machined component (metal element 3a).
Although such abnormal shaped portions can be reduced to a negligible level, for example barrel processing, this requires so many man-hours to the point it causes a new inconvenience.
Therefore, it is an object of the present invention to provide an inspection method which can achieve sufficient reliability of a continuously variable transmission belt without spending much working time.
In accordance with the present invention, there is provided an inspection method of a continuously variable transmission belt assembled through supporting the element laminated body constituted of a number of metal elements on belt laminated bodies constituted of a plurality of steel belts, wherein the inspection method comprises: a trial step in which an continuously variable transmission belt in assembled state is tried with load applied; a separation step in which the belt laminated body and the element laminated body are separated from each other after completion of the trial step; and an inspection step in which the steel belt positioned in the first layer of the belt laminated body separated in the separation step is inspected whether there is any damage on the surface thereof.
According to the invention, the belt laminated body is separated from the continuously variable transmission belt after the trial use is carried out with the load applied, and an inspection is carried out as to whether there is any damage on the surface of the steel belt positioned in the first layer of the belt laminated body.
Thus, if a metal element which includes an abnormal shaped portion (see element 3i in FIG. 2(a)) is mixed in the metal elements constituting the element laminated body, and if the abnormal shaped portion is not negligible because it adversely affects durability of the continuously variable transmission belt, damage (or scar) highly probably occurs on the surface of the steel belt positioned in the first layer of the belt laminated body. Accordingly, by monitoring to find the damage (or scar), a defective continuously variable transmission belt can be identified before it is mounted to the continuously variable transmission, whereby only a good continuously variable transmission belt can be mounted to the continuously variable transmission. As a result, a process which requires much working time such as barrel processing can be eliminated or even when the process is simplified, occurrence of problems in the continuously variable transmission can be prevented to achieve sufficient reliability.
In accordance with the preferred mode of the present invention, the inspection step is carried out as to detect whether there is any damage on the surface of the steel belt by an image recognition technology or other nondestructive inspection technologies.
In this case, as the other nondestructive inspection technologies, there are magnetic particle inspection, liquid penetrant inspection, eddy current inspection, radiographic inspection, ultrasonic inspection, probe surface inspection, and so on.
In the trial step, the trial use is carried out by laying the continuously variable transmission belt of the assembled state on a driving pulley and a driven pulley of the continuously variable transmission or two pulleys similar to the two pulleys, and applying a driving force on one pulley and a load on the other pulley. When the trial use is carried out, the diameter of either the pulley with the driving force applied or the pulley with the load applied is reduced.
The load in the trial step is a load close to a real use environment of the continuously variable transmission belt or a load imitating the real use environment.
The above and further objects and novel features of the present invention will more fully appear from the following detailed description when the same is read in conjunction with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not intended as a definition of the limits of the invention.